In accordance with known case-ready fresh meat packaging techniques, fresh meat products are processed from primals into various cuts at the meat processing plant where they are then packaged prior to shipment to the retail market. The packaging step typically includes placing the cuts within a styrofoam tray which is overwrapped with a non-barrier clear plastic film. The overwrapped trays are then placed within a vacuum packed and gas-flushed barrier bag. The above described packaging technique is typically done in the normal nitrogen-oxygen atmosphere of the meat packing facility. Such packaging typically only has a shelf life of between ten to fifteen days. This relatively short shelf life is due, in large part, to the prolonged exposure of the meat to the residual oxygen that is present in the packaging.
Prolonged exposure of fresh meat to oxygen is known to cause bacterial decay and discoloration of the meat. Also, conventional fresh meat packaging is very sensitive to temperature variations, thus requiring careful handling of the packaged meat products during transport to the retail display case.
In the case of red meat, in particular, prolonged exposure to oxygen causes the conversion of myoglobin meat pigmentation to the grey or brown metmyoglobin, which is generally unacceptable for the average retail customer. However, a controlled exposure of the meat product to oxygen is necessary in order to oxygenate the meat pigment to bright red oxymyglobin. This creates the desired red "bloom" of the meat which the average retail customer associates with freshness and wholesomeness.
It is known in the art to package fresh meat in a modified atmosphere environment whereby the packaging is flushed with a preservation-enhancing gas mixture, typically containing a bacterial inhibitor such as carbon dioxide. In the case where styrofoam packing trays are used, however, residual oxygen is trapped inside the porous openings of the styrofoam tray material and eventually diffuses out over time, thereby causing premature discoloration and bacterial decay of the meat.
U.S. Pat. Nos. 4,685,274 and 5,226,531, both issued to Anthony J. M. Garwood, disclose a packaging system for fresh meat which utilizes a specially constructed retail case-ready tray for prolonging the shelf life of the fresh meat product. Garwood teaches that the tray may be constructed of a gas barrier plastic material. The packaging system of Garwood further includes a laminated web of gas permeable clear flexible plastic wrap material which seals the meat within the tray and a lid which forms a domed enclosure over the laminated web. In use, the packaging is evacuated of normal atmosphere and is flushed with a gas mixture of carbon dioxide and nitrogen to preserve the contents. When the dome is pulled off, oxygen is allowed to contact the meat and the product blooms.
Under ideal storage conditions (ie., where storage temperature is maintained between 29.degree. F. and 32.degree. F.), the Garwood packaging system is able to achieve a shelf life in a range of about twenty to forty days. The maximum shelf life for the Garwood packaging system, however, is determined by the maximum amount of carbon dioxide that can be practicably stored within the domed enclosure, which is typically only 60-70% by volume of the total gas mixture. Nitrogen, or some other like inert gas, must be used as a filler, otherwise the packaging will implode as the meat absorbs the carbon dioxide within the limited volume domed enclosure.
Another drawback of the Garwood packaging system is that the addition of the special lid for forming the domed enclosure increases the overall cost of the packaging over conventional plastic overwrapped trays. For many retailers, the benefit of the increased shelf life does not outweigh the additional cost incurred by the packaging. A less expensive packaging which also affords increased shelf life would be desirable.
Further, it would be desirable to be able extend the shelf life of the packaged meat beyond the present maximum shelf life of about twenty to forty days, and preferably, up to a maximum shelf life of sixty or even ninety days.